Showing posts with label hydrogen. Show all posts
Showing posts with label hydrogen. Show all posts

Wednesday, June 27, 2018

'Electrogeochemistry' captures carbon, produces fuel, offsets ocean acidification

Researchers analyze global potential for 'negative emissions energy' using electricity from renewable sources to generate hydrogen fuel and capture carbon dioxide.

Greg Rau with a monument in the background marking
the Arctic circle along the unfrozen coast of Norway 
Limiting global warming to 2 degrees Celsius will require not only reducing emissions of carbon dioxide, but also active removal of carbon dioxide from the atmosphere. This conclusion from the Intergovernmental Panel on Climate Change has prompted heightened interest in "negative emissions technologies."

A new study published June 25 in Nature Climate Change evaluates the potential for recently described methods that capture carbon dioxide from the atmosphere through an "electrogeochemical" process that also generates hydrogen gas for use as fuel and creates by-products that can help counteract ocean acidification.

First author Greg Rau, a researcher in the Institute of Marine Sciences at UC Santa Cruz and visiting scientist at Lawrence Livermore National Laboratory, said this technology significantly expands the options for negative emissions energy production.

The process uses electricity from a renewable energy source for electrolysis of saline water to generate hydrogen and oxygen, coupled with reactions involving globally abundant minerals to produce a solution that strongly absorbs and retains carbon dioxide from the atmosphere. Rau and other researchers have developed several related methods, all of which involve electrochemistry, saline water, and carbonate or silicate minerals.

"It not only reduces atmospheric carbon dioxide, it also adds alkalinity to the ocean, so it's a two-pronged benefit," Rau said. "The process simply converts carbon dioxide into a dissolved mineral bicarbonate, which is already abundant in the ocean and helps counter acidification."

The negative emissions approach that has received the most attention so far is known as "biomass energy plus carbon capture and storage" (BECCS). This involves growing trees or other bioenergy crops (which absorb carbon dioxide as they grow), burning the biomass as fuel for power plants, capturing the emissions, and burying the concentrated carbon dioxide underground.

"BECCS is expensive and energetically costly. We think this electrochemical process of hydrogen generation provides a more efficient and higher capacity way of generating energy with negative emissions," Rau said.

He and his coauthors estimated that electrogeochemical methods could, on average, increase energy generation and carbon removal by more than 50 times relative to BECCS, at equivalent or lower cost. He acknowledged that BECCS is farther along in terms of implementation, with some biomass energy plants already in operation. Also, BECCS produces electricity rather than less widely used hydrogen.

"The issues are how to supply enough biomass and the cost and risk associated with putting concentrated carbon dioxide in the ground and hoping it stays there," Rau said.

The electrogeochemical methods have been demonstrated in the laboratory, but more research is needed to scale them up. The technology would probably be limited to sites on the coast or offshore with access to saltwater, abundant renewable energy, and minerals. Coauthor Heather Willauer at the U.S. Naval Research Laboratory leads the most advanced project of this type, an electrolytic-cation exchange module designed to produce hydrogen and remove carbon dioxide through electrolysis of seawater. Instead of then combining the carbon dioxide and hydrogen to make hydrocarbon fuels (the Navy's primary interest), the process could be modified to transform and store the carbon dioxide as ocean bicarbonate, thus achieving negative emissions.

"It's early days in negative emissions technology, and we need to keep an open mind about what options might emerge," Rau said. "We also need policies that will foster the emergence of these technologies."

In addition to Rau and Willauer, coauthor Zhiyong Jason Ren at the University of Colorado in Boulder (now at Princeton University) also contributed to the paper. This work was supported by Lawrence Livermore National Laboratory, Office of Naval Research, and National Science Foundation.


• 'Electrogeochemistry' captures carbon, produces fuel, offsets ocean acidification, News release by Tim Stephens at UC Santa Cruz

• The global potential for converting renewable electricity to negative-CO2-emissions hydrogen, by Greg H. Rau, Heather D. Willauer, Zhiyong Jason Ren.

• Olivine weathering to capture CO2 and counter climate change

• Climate Plan

See comments at the facebook geoengineering group

Monday, April 18, 2016

Can we Design Hydrogen-Fuelled Aircraft?

Can we Design Hydrogen-Fuelled Aircraft?

S H Salter, Engineering and Electronics, University of Edinburgh.EH9 3JL.

The collection of temperature measurements by David Travis following the 3-day grounding of all US civilian flights after 9/11 showed the astonishing effect of jet exhaust on the environment. If burning hydrocarbon fuel in the stratosphere ever becomes a criminal offence, the aviation industry will have an interesting problem. A possible solution is the use of hydrogen as a fuel. Is this technically possible?

The Airbus 380 carries 250 tonnes of fuel with a total calorific value of about 1013 joules. Fuel is stowed in wing tanks but this would be a volume of about one eighth of the fuselage. The calorific value per unit mass of hydrogen is about 3.5 times that of jet fuel and so the weight of hydrogen for the same range would be only about 70 tonnes. Unfortunately the ratio of density of jet fuel to un-pressurized hydrogen is about 9000, so the design problem is how to reduce the volume ratio by about 2500. If we compress hydrogen to reduce its volume by a factor of, say, 100 we still have a fuel volume of 25 times the liquid fuel one or 3.2 times the fuselage volume. The cube root of 3.2 is 1.47 so by increasing all three fuselage dimensions by this factor we could have an aircraft with enough volume for all fuel in the fuselage but no passenger space. An increase by a factor of about 1.6 in both diameter and fuselage length would give enough volume for passengers provided they did not feel unhappy about being close to so much hydrogen.

The immediate reaction against the proposal will be triggered by embedded folk memories of the Hindenburg. Any use of hydrogen will need careful public relations. The Hindenburg survival rate was 64%, much better than crashes of modern conventional aircraft. Deaths were caused by jumping not burning. People who stayed aboard until the wreck reached the ground were unharmed. It is likely that the fire started in the fabric dope rather than the hydrogen. Because spilt hydrogen moves rapidly upwards there is much less risk than from a liquid fuel or heavier-than-air gases like butane or propane which regularly cause devastating explosions in boats and buildings. Furthermore the heat radiated by the invisible hydrogen flame is much lower than that from carbon particles in hydrocarbon flames. We can argue that hydrogen is actually safer than jet fuel, petrol and hydrocarbon gases.

We can spend the 180 tonne fuel weight-saving on gas storage bottles in the form of a low-permeability skin surrounded by wound carbon fibres. A helical winding of aluminium sheet with a low diffusion coefficient for hydrogen looks good. It can be made with the linear equivalent of spot welding. The axial stress in a thin-wall tube under pressure is only half the hoop stress, so we can use the gas tubes as fuselage strength-members. Once the fuselage bending moments are known, we can choose the wrap angle of the windings to give the right balance of directional strength. One structure might be a bundle of nine tubes in a hexagonal array with six full of hydrogen and three containing passengers. A cross section is sketched in the figure. Other configurations are being studied.

The smooth stress paths of the gas bottles would be badly disrupted by the conventional design of landing gear. Can we get rid of it? The requirements for processing the variable energy flows from renewable-energy sources have led to the development of new high-pressure oil machines using digital rather than analogue control of machine displacement. These machines have very high conversion efficiencies and very easy interfaces to computers (see ) . The extremely accurate control of very large energy flows allows many new applications. One of these involves replacing the landing gear of large passenger aircraft with a ground vehicle. Please suspend disbelief until you have considered the following facts:
  1. The landing gear of the A380 weighs 20 tonnes, say, 200 passengers. This weight is carried round the world for many hours and then used for only a few minutes on each flight.
  2. The landing gear occupies a substantial volume of the internal space. The volume restriction limits the travel of the landing gear and so increases acceleration forces.
  3. The requirement for openings compromises the structural integrity of the fuselage and adds weight, even more passengers.
  4. Landing gear must perform with very high reliability despite the weight penalty and extreme temperature cycling.
  5. The full weight of the aircraft must be passed to the ground through highly stressed points.
  6. Gas turbines are very inefficient for moving aircraft on the ground at slow speeds.
  7. On the A380 the shape of the landing gear doors and opening spoils the aerodynamic fairness. 
  8. There is a severe design conflict between tyre weight, tyre life and braking performance.
An alternative might be to provide the function of the landing gear by a special-purpose ground vehicle. It would of course have to have VERY reliable links to the aircraft ground approach electronics so as to be in exactly the right place and moving with the right velocity underneath an aircraft on final approach. However there would be no weight, volume or temperature compromises.

The contact between the landing vehicle and the aircraft would be provided by a nest of large air-filled tubes like very large, very soft V-block, running the full length of the fuselage. This would spread the weight evenly into the aircraft skin. The tube surfaces could have vacuum suckers, like an octopus, which could apply shear forces evenly to the aircraft skin. The bags could be on a frame which could have hydraulic actuators to give a much longer travel than the legs of the landing gear. Tilting this frame would remove the need for the angling of the rear underside of the fuselage required to prevent ground contact at V-Rotate. This would further reduce drag during flight. The absence of fuselage penetrations could allow safe water landings for emergency. Runways can have parallel lakes presenting a much lower fire hazard if fuel is spilt. The impact loading on the runway would be much reduced and it might even be possible to revert to grass runways with several parallel operations from any wind direction.

The ground vehicles could use Diesel engines with much higher efficiency at taxi speed than gas turbines. They could have higher acceleration during take off and higher deceleration during landing. The hydraulic transmission would also allow regenerative braking, so the kinetic energy from one landing could be used for the next take-off. All-wheel steering and the option of direct side movement would allow much better use of ground space. The ground vehicle could have many more tyres, which need have no weight or volume compromise to achieve high braking. It could have an air-knife to dry runway surfaces and remove snow. There would be plenty of time to inspect and exchange landing vehicles and they would be in use for a much higher fraction of the time. The landing vehicles could gently lower aircraft on to passive supports at each loading pier and be used for other movements while aircraft were being boarded or serviced.

Images by S H Salter, University of Edinburgh.
The volume of most aircraft wings is much below that of the fuselage and so there is not a strong reason to use gas tubes as structural wing members. However they would offer a way to offset the extra drag of the larger frontal cross-section. From the original work by Prandtl, it has long been known that sucking air from the upper surface of an aerofoil section will reduce the drag by an amount which far offsets the power needed for a suction pump. Schlichting in figure 14.9 of Boundary Layer Theory gives a graph showing a factor of more than two. An objection to suction on wings, where the outer skin is a structural member, is that perforations and slits cause stress concentrations. This should not apply to wing spars made as gas tubes supporting an unstressed skin.

It is important that using fuel does not move the centre of gravity of the aircraft. This happens automatically with fuel stowed in wing tanks. If large quantities of fuel are to be stored in the fuselage it will be necessary to have the centre of pressure of the wings close to the centre of gravity of the fuselage-engine combination. The choice of a ground-based landing vehicle suggests high wings and engine placement above the wing. In theory at least, this will give some advantage from higher air-velocity over the upper wing surface and lower noise transmission to ground level. It is much easier to service and inspect equipment if you do not have to reach above your head. Cranes lifting an engine upwards are much more convenient than forklift trucks working from below. While some change in the architecture of maintenance hangers would be required, high engines accessed from above would by no means be unwelcome to ground crew.

Gas tubes may not be ideal for connections to a low-chord wing and so the longer attachment line of a delta wing, such as used in the Vulcan and Concord and many fighter designs, should be investigated. A flat underside will relax the requirement for precision in yaw during landing. Suction may be able to offset some of the disadvantages of the delta wing as applied to civilian aircraft provided always that they can land safely after a failure of the suction system. A delta wing with a deep thickness and a leading edge made from very strong but transparent material, perhaps poly carbonate, might even allow passengers to sit in the wing enjoying a splendid view if their vertigo allows.

The range of the A 380 is 15,000 kilometres. While this may have been chosen for passenger convenience with the properties of present fuels, it is larger than necessary for trans-Atlantic flights and could allow a further volume reduction. The San Francisco to Sydney distance is only 12000 km and stops in mid Pacific could be very attractive.

Before we waste time on radical new aircraft designs and ground-based landing systems, it is necessary to confirm that burning hydrogen in gas turbines at high altitudes will be a chemically appropriate solution. If we burn hydrogen in ambient air there will be no release of carbon dioxide but there will still be the formation of nitrogen–oxygen compounds collectively known as NOXes. If these are cooled very rapidly, as in the adiabatic expansion of an internal combustion engine, they can be ‘frozen’ at the high-temperature equilibrium state with lots of very nasty acids. The lower combustion pressure and slightly slower cooling of a jet exhaust should be less severe but we want to quantify the severity of the problem. There may even be problems from ice crystals formed from the exhaust. I have asked colleagues at the National Centre for Atmospheric Research at Boulder Colorado for an opinion.

There is one engine design in which the combustion products cool slowly enough for almost all the NOX production to revert to ambient values. This is the Stirling engine originating from 1815 but abandoned because of the absence of materials with good thermal conductivity and high hot strength. Much better materials are now available. By an extraordinary coincidence, the digital hydraulic systems needed for the speed and accuracy of the ground-based landing gear can also radically change the design of Stirling engines by using hydraulics to replace the crank and connecting rods of the conventional Stirling engine. A Stirling-engined aircraft would probably have to use a ducted fan or propeller propulsion but these could still allow civilian aviation to continue in a NOX-sensitive world.

The best way to do experiments on high-altitude engine-chemistry might be from a balloon. Do we know anyone with an interest in this area?

Monday, October 19, 2015

Lucy-Alamo Projects - Hydroxyl Generation and Atmospheric Methane Destruction

As you know the weather is starting to change rapidly for the worse now and I have been working on Arctic methane induced global warming for about 14 years. There are massive deposits of methane gas trapped in the undersea permafrosts in Russian waters and onland in Siberia as well and if the global warming boils of just 10% of what is there, there is enough to cause a Permian style extinction event that humanity will not survive. Some brilliant work on the Arctic methane threat has been done by a Russian scientist Natalia Shakhova and others who indicate that we are in a very perilous position, if we don't find a way of reducing the atmospheric methane and depressurizing the undersea methane to stop the massive methane eruptions there. I and some other workers have designed a radio-laser Atmospheric methane destruction system based on the early Russian radio-wave induced conversion of methane to nano-diamonds. This radio-laser system can be installed on nuclear powered boats such as the 40 Russian Arctic ice breakers and start immediate work on destroying the atmospheric methane clouds that are building up in the Arctic. An abstract about the system is attached and it has been accepted for presentation at a congress of the American Meteorological Society to be held on January 10 - 14, 2016 at New Orleans in Louisiana, U.S.A. This system should be mounted on the nuclear icebreakers and used onshore. Once the methane is brought under control there should be a reduction in the massive fire hazards, heat waves and severe storms systems that are plaguing Russia and the rest of the world.

Yours sincerely,

Malcolm P.R. Light
Earth Scientist

The Abstract follows:-
No. 275345 Lucy - Alamo Projects - Hydroxyl Generation and Atmospheric Methane Destruction.
Malcolm P.R. Light (Dr)
Retired, Cortegana, Spain

Congress of the American Meteorological Society, Wednesday 13, January, 2016

Methane formed by organisms in the water becomes trapped in the fabric of water ice crystals when it freezes and is stable below about 300 metres depth in the Arctic Ocean and on the shallow East Siberian Arctic Shelf. There are such massive methane reserves below the Arctic Ocean floor, that they represent 100 times the amount, that is required to cause a Permian style major extinction event, should the subsea Arctic methane be released into the atmosphere because of methane's giant global warming potential (100 to 1000 times CO2) over a short time period (Light and Solana, 2012 - 2014, Carana 2012 - 2014). There are also giant reservoirs of mantle methane, originally sealed in by shallow methane hydrate plugs in fractures cutting the Arctic seafloor and onshore in N. Siberia (Light, 2014, Carana 2013, Light, Hensel and Carana, 2015). The whole northern hemisphere is now covered by a thickening atmospheric methane global warming veil from Arctic methane emissions at the level of the jet streams, which is spreading southwards at about 1 km a day and already totally envelopes the United States (Figure 1). There must therefore be a world-wide effort to capture and thus depressurise the methane in the subsea and surface Arctic permafrost and eradicate the quantities accumulating in the ocean and atmosphere.

Methane produced at the surface diffuses upward and is broken down by photo dissociation (sunlight) and chemical attack by nascent oxygen and hydroxyl (Heicklen, 1967). The Lucy Project is a radio/laser system for destroying the first hydrogen bond in atmospheric methane when it forms dangerously thick global warming clouds over the Arctic (Figure 2, Light & Carana, 2012). It generates similar gas products to those normally produced by the natural destruction of methane in the atmosphere over some 15 to 20 years. Radio frequencies are used in generating nano-diamonds from methane gas in commercial applications over the entire pressure range of the atmosphere up to 50 km altitude (Figure 2, Light and Carana, 2012). Recent experiments have shown that when a test tube of seawater was illuminated by a polarized 13.56 MHZ radio beam, that flammable gases (nascent hydrogen and hydroxyls) were released at the top of the tube (, 2013). In the Arctic Ocean, polarized 13.56 MHZ radio waves will decompose atmospheric humidity, mist, fog, ocean spray and the surface of the waves themselves into nascent hydrogen and hydroxyl over the region where a massive methane torch (plume) is entering the atmosphere, so that the additional hydroxyl produced will react with the rising methane, breaking a large part of it down (Figure 2)(, 2013).

A better system could use Nd: glass heating lasers containing hexagonal neodymium which is stable below 863oC (Krupke 1986 in Lide and Frederickse, 1995). Neodymium glass lasers have extreme output parameters with peak powers near 10 to the power 14 watts when collimated and peak power densities of 10 to the power 18 watts per square cm if focused (Krupke 1986 in Lide and Frederickse, 1995). Velard (2006) states that at the Lawrence Livermore Laboratory, for inertial confinement nuclear fusion, "192 beams of Nd: glass - plate amplifier chains are being used in parallel clusters to generate very high energy (10 kilojoules) at a very high power (>10 power 12 watts) and at the second and third harmonics of the fundamental, with flexible pulse shapes and with sophisticated spectral and spacial on - target laser light qualities". The Nd: glass laser system is more stable and efficient than the longer wavelength CO lasers and shorter wavelength KrF lasers (Velard, 2006).

The three 13.56 MHZ radio transmitters in the Lucy Project (Figure 2) could be replaced by 3 groups of parallel lasers each forming a giant circular flash lamp. Half the Nd: glass lasers in the flash lamp could be tuned to exactly 21 million times the 13.56 MHZ methane destruction/nano-diamond formation frequency (Mitura, 1976). The adjacent alternate lasers will be tuned to a slightly different frequency exactly out of phase with the primary frequency by 13.56 MHZ.The Nd: glass lasers have a wavelength of 1052 nm equivalent to a frequency of 2.85*10 power 8 MHZ. The methane molecule requires 435 kilo-joules per mole to dislodge the first hydrogen proton and an average of 409.3 kilo - joules per mole for the other three protons (Hutchinson, 2014). Hydroxyl requires 493 kilo - joules per mole to generate it from water (Hutchinson, 2014). A set of four focused Nd; glass lasers will have an energy of about 454.5 kilo-joules per mole, and will be strong enough to dislodge the first hydrogen proton from a methane molecule. Of course this can also be achieved by increasing the number of focused lasers to six or eight. Exactly the same neodymium laser system could be shone on the sea surface, at the base of the rising methane cloud, generating hydroxyls and nascent oxygen and thus breaking down the methane. The power source for these radio transmitters/lasers in the Arctic can come from floating or coastal nuclear or gas electric power stations and the transmitters could be located on shore or on boats, submarines, oil-rigs and aircraft. We have only 1 to 5 years to get an efficient methane destruction radio-laser system designed, tested and installed (Lucy and Alamo (HAARP) projects) before the accelerating methane eruptions take us into uncontrollable runaway global warming. Humanity will then be looking at catastrophic storm systems, a fast rate of sea level rise and coastal zone flooding with its disastrous effects on world populations and global stability.


- Lucy-Alamo Projects - Hydroxyl Generation and Atmospheric Methane Destruction, by Malcolm P.R. Light (Dr) Light

- North Siberian Arctic Permafrost Methane Eruption Vents, by Malcolm P.R. Light, Harold H. Hensel and Sam Carana 

- Poster created for Geophysical Congress on methane hydrates, earthquakes and global warming, Nice, France, 2002, by Malcolm Light and Carmen Solana

Poster Presentation at American Meteorological Society's 18th Conference on Atmospheric Chemistry, January 10 - 14,...
Posted by Sam Carana on Monday, October 19, 2015